Prior to the advent of satellite-synchronized clocks, a ship's clock would be synchronized to the average time of all wrist watches onboard. If some watches were running fast and others were running slow, the average of the group would be expected to be relatively stable over time.
The above practice led to “parity space” for tracking average environmental parameters for large, complex systems such as nuclear reactors. For example, one may average all temperature sensors aggregated across a system, and use that as the mean temperature for the system. One may then monitor differences between individual signals and this global average as a means of detecting sensor drift and/or thermal anomalies. With this technique, internal diagnostics may be made relatively immune to large-scale changes in ambient temperatures.
Conventional computing system thermal management practices may set threshold limits in servers so that if a component temperature exceeds some threshold, e.g., 85° C., a warning is generated or the component is shut down to avoid thermal damage. If one were to merely apply threshold limits to temperature sensors throughout a system and ambient temperatures were to change (because of temporary problems with datacenter air conditioning systems, a step change in temperature following installation of a new rack of servers, etc.), then the thresholds could be exceeded even though individual severs were not experiencing internal thermal events. Parity space techniques, as described above, may be used to make these thermal management practices more immune to variations in ambient temperatures.